1. Field of the Invention
The present invention relates to technology for combining a plurality of images in which adjacent images have a common subject region and generating a synthesized image.
2. Description of the Related Art
Hitherto, the synthesis of a panoramic image by combining a plurality of images is performed by a conventional method of capturing images of a subject in a plurality of regions and synthesizing a single image using image information about a common subject region, as shown in FIG. 10. FIG. 11 shows a sectional view taken through the XZ plane of FIG. 10. As shown in FIG. 11, an image synthesis method includes a mode (planar mapping mode) of mapping captured images onto a single plane 800 and synthesizing an image or a mode (cylinder mapping mode) of mapping the images onto a virtual cylindrical surface 801 having a radius f and synthesizing an image. FIG. 12 schematically shows a synthesized image obtained when the images are mapped onto the plane 800.
In the conventional panoramic image synthesis method, it is necessary to synthesize an image in a predetermined mapping mode. Alternatively, a user is required to manually set a mapping mode.
For example, when a plurality of images captured by horizontal panning are combined into a synthesized image in the planar mapping mode, as shown in FIG. 12, an image with distorted edges is generated due to a wide horizontal viewing angle. When a synthesized image is formed on a region in which the horizontal viewing angle is 180° or greater in the planar mapping mode, the synthesized image cannot be mapped on a single plane, possibly causing a serious apparatus failure.
It is burdensome to conform to various imaging modes, i.e., a horizontally-rotating (panning) mode shown in FIG. 10, a vertically-rotating (tilting) mode, and a horizontally/vertically-rotating (panning/tilting) mode, and to designate an appropriate mapping mode from among these mapping modes. When the user is not knowledgeable about these mapping modes, the user may fail to select the appropriate mapping mode.
In the conventional panoramic image synthesis method, an appropriate mapping method is selected and set prior to generating necessary parameters for synthesis processing. Using this mapping method, an input image is mapped and transformed. Subsequently, the parameters indicating the positional relationship among a plurality of images are generated based on corresponding point information, and a synthesized image is generated.
When the mapping method is subsequently changed and a synthesized image is again generated since the previously-selected mapping mode is inappropriate, it is necessary to re-input the images, to perform mapping transformation in another mapping mode, and to perform complicated image synthesis processing. In other words, it is necessary to again perform processing from the beginning to generate the parameters. This places a heavy computational burden on the apparatus, requires a long processing time, and is extremely inefficient.